1. Field of the Invention
The small-sized simple switch for protecting circuit of the present invention relates to a circuit protection device which is simple in structure and used to control ON/OFF of a circuit and, in particular, to a switch which automatically trips for circuit protection during power overload and which resets the circuit to the original "ON" condition only after the user depresses a reset button on the switch.
2. Description of Related Art
Conventional switches for indoor use or for use on electrical appliances are of the pressing type which effect switching between the closing and opening of a circuit by depressing a switch's ON/OFF button. However, these switches only serve the function of switching between the closing and the opening of a circuit and can not ensure safety for power supply for these switches do not automatically trip or cut off the power supply for circuit protection when a power overload exists.
In U.S. Pat. No. 5,262,748 issued on Nov. 16, 1993 (see FIG. 1), a switch for circuit protection is disclosed in which an n-shaped spring plate 11 springs up when the power is overload and then an alloy plate 13 is moved up by an actuating lever 12, causing contacting points 14, 15 to become disengaged. With this switch, in addition to requiring the n-shaped spring plate 11, another support lever 17 is connected under the center of a pressing portion 16 and a round head 171 of the support lever is embedded in a braking slot 18 so as to control the swing of the support lever 17 back and forth such that both the structure and the operation of the switch are rather complicated. In RON application Pat. No. 82,204,642 published on Jun. 21, 1993 (see FIG. 2), another switch for circuit protection is disclosed in which an arcuated resilient plate 21 is pivoted to a contact spring plate 22 and abuts against an actuating plate 24 when the platinum contacting point 221 of the contact spring plate 22 is in contact with the platinum contacting point 231 of an wire connecting pad 23. The structure of this switch is also complicated. In U.S. Pat. No. 5,760,672 issued on Jun. 2, 1998 (see FIG. 3a), a further switch for circuit protection is disclosed in which no n-shaped spring plate, or arcuated resilient plate is used as disclosed in the previous patents, but an upper supporting lever 32 and a lower supporting lever 33 are provided at a proper distance above and under the arc changing position, respectively, on the disk-shaped bimetal alloy plate 31 in the switch body functioning as a seesaw, which, together with a lever 34 having a tripping space, cause the disk-shaped bimetal alloy plate 31 functioning to trip in both directions, thus effects the closing and opening of the circuit by pushing or pulling actions. Moreover, the alloy plate used in this patent is a relatively complicated disk-shaped bimetal alloy plate 31. As shown in FIG. 3b, the disk-shaped bimetal alloy plate 31 is structured with its central face extending from a free end to a fixing end into a contact spring plate 311, the contact spring plate 311 being provided on the extremity with a platinum contacting point 3111 for contact with the platinum contacting point 312. Then, the disk-shaped bi-metal alloy plate 31 is formed into the configuration with a wider free end and a narrower fixing end (W1&gt;W2). As a result, when the fixing end of the disk-shaped metal alloy plate 31 is reduced to a smaller width (W2), the internal stress causes it to deform into an arcuated dish-like shape, and then, in combination with the upper and lower supporting levers 32, 33, it is possible to effect tripping for circuit protection power current overload. U.S. Pat. No. 5,828,284 issued on Oct. 27, 1998 (see FIG. 4) discloses another safety switch for overload protection. It can be seen from FIG. 4 that a resilient member 41 (a spring) engaging a driving member 42 is used in the switch, the driving member 42 being connected to a pressing portion 43 above and to a lead plate 44 below, such that when the lead plate 44 is overheated and becomes deformed, the pressing portion is pushed up, causing the switch to open for circuit protection. This switch, however, is also rather complicated in that a resilient member and the like are used.
From the foregoing, it can be seen that conventional circuit protection switches are all implemented by using a complicated structure which increases the cost.